Microwave Propagation and Remote Sensing

Preface

Radio wave is a term arbitrarily applied to electromagnetic waves in the frequency range 0.001 to 10¹⁶ Hz. The lower limit of radio waves propagated in free space is 3 × 10¹¹ m and the upper limit is 3 × 10^–8 m. It is relevant to note that these limits of the radio wave spectrum are considerably wider than they were assumed to be until quite recently. In the low frequency side, for example, 0.001 Hertz (H₂) is an arbitrary limit, for as science advances one will have to deal with the progressively lower frequency side. But, on the high frequency side the radio wave spectrum limited to 10¹² Hz was called submillimeter wave. However, from the engineering point of view, the wave of frequency ranging from 3 to 300 GHz may sometimes be ...